Intro: The Question of Living in Space

I have been giving much thought of late to the issue of space settlement
architecture and the rather obvious lack of realistic portrayals of such in
the contemporary media. Portrayals of space outpost architecture are common
and have been for many decades but not true settlements and, though often
regarded as roughly the same thing, the two are radically different in
program and hence ultimate design and appearance.

An outpost is a logistical component in a campaign of exploration and its
design is dominated by the requirements of quick deployment in uncertain
environmental conditions without the benefit of an established
infrastructure. One doesn't know exactly where one might end up when
initially traveling to a frontier and so one must rely on portable shelter
with great built-in capability and ruggedness often at the cost of comfort.
The more hazardous and barren the environment anticipated the more robust
such shelter must be. The environments of space are so hazardous that
outpost shelters are effectively spacecraft in every way but propulsion, and
sometimes temporary components of a spacecraft or, in some recent designs,
even taking the form of surface vehicles as well. Hence the 'tin can'
habitats based on monocoque spacecraft hull structures that have been
ubiquitous in space art since the days of Von Braun. There is no concern for
economic/industrial sustainability for the outpost as it is supported almost
entirely from a distance and often regarded as temporary and disposable.
It's not intended to 'pay for itself' except by the information the
exploration campaign ultimately communicates back to its sponsors. Though it
might employ local resources, during an initial exploration campaign the
lack of assessed resources and industry to process them as well as the high
premium on manual labor limits one to the most basic of resources with
minimal processing. In space that's dirt, sunlight, and the ambient
atmosphere if there is one.

A settlement is focussed on permanent habitation and the systematic
exploitation of specific local resources. It's location is specifically
chosen, based on the information gained in an exploration campaign, for
optimal access to resources and transportation connections. It's designed to
be permanent, its priority industrial/economic sustainability. Put simply,
it's a place to stay, not to visit. It must be created from and sustain
itself primarily using local resources and/or by exporting them in processed
form for profit to pay for imported materials -which in the context of space
is a dubious proposition since most materials elsewhere in the solar system
aren't worth the cost of their transport to the Earth using existing
transportation technology. (space tends to be more valuable as a place to
process things in its special environment rather than as a source of any
material)

Challenging profitability and a need for high transport volumes also compels
reliance on lowest cost/highest efficiency means of transportation for what
import goods local materials and industry cannot provide. 'Soft' landing
spacecraft, as we typically see portrayed with outposts, will be limited to
the most delicate of cargo (human beings primarily) because of high
operational cost. Until more mass produced vehicle systems based on the kind
of standardization of terrestrial container shipping became available,
everything else would likely employ unmanned transport and delivery by
'rough' lander systems akin to the parachute drop methods of military
re-supply -most likely systems like the ballistic entry air-bag landing
methods of recent space probes and similarly disposable tethered thruster
drop systems. (a system for airless environments where a simple rocket
carriage takes the place of a parachute for a cargo container or pallet on
the end of a tether) This limits import goods to highly modular durable
items in 'knockdown' and containerized forms that can be tightly packed to
minimize damage in delivery and which can tolerate space environments during
transport from Earth without much protection.

A settlement must also offer an unlimited potential for comfort and luxury
despite its reliance on low cost construction as an incentive to the
prospective settler -a critical issue we don't often see discussed in the
space advocacy community. People settle new places because they anticipate a
practical advantage to going there, either in the form of wealth that can be
earned and sent back 'home' or invested in a progressively higher quality of
life in their new home. That is the whole point to settling a new frontier.
This latter requirement may be the key reason we don't see a serious
exploration into realistic settlement design. This is because, when one
seriously investigates this, one is immediately confronted by one simple
fact that contradicts most notions of a normal quality of life; that living
permanently in space basically means living one's entire life indoors.

The common sci-fi image of astronauts romping around in space suits all the
time is unrealistic because space suits are too expensive, too short-lived,
too dependent upon a very sophisticated and large industrial infrastructure
for their manufacture, and too inadequate in radiation shielding. Space
explorers can get away with such activity because they aren't living in
space. They only visit there and so the relatively high radiation exposure
during their mission time is small relative to their life span. The
permanent space settler will be required to closely monitor his radiation
exposure life-long as it will severely limit his range of activity and
effective number of working years if not minimized. Settlement structures
will have to be much more heavily shielded than outpost structures and
outdoor activity strictly limited. It's likely that the only times most
space settlers will wear a space suit is when performing emergency training.

Routine outdoor activity will have to be conducted telerobotically, both for
safety reasons and because robots are more cost-effective than space suits
by virtue of lower production cost, less sophisticated fabrication, longer
duty life, and easier repair. The issue of human superiority over robots
-often the object of much argument in space advocacy circles- is irrelevent.
The economics of the EVA are simply untenable so it becomes more practical
to engineer routine tasks around the more cost-effective tools. Every
industrial designer understands the logic of this but it has long escaped
people in the space programs. Of course, as a settlement becomes more robust
and industrially capable the cost of space suits comes down as they can be
fabricated and repaired locally, as does the cost of power which may be used
to deploy recently speculated artificial magnetosphere systems providing
large area radiation shielding. This may make more frequent EVAs practical
over time. But in the near term the economics of the EVA do not seem likely
to change much.

To complicate things further, shielding and cost issues will also tend to
preclude the use of windows in space settlement structures. The cost of
import goods in space is determined more by their mass than by their
composition or manufacturing sophistication. A roll-up plastic laminate
video display is less expensive to import to Mars and safer to deliver to
its surface than a simple but heavy pane of window grade glass or
polycarbonate, despite the fact that such a display might be much more
expensive to manufacture in comparison. So aside from very small view ports
around hatches and utility structures, the most practical type of windows in
this environment are virtual ones, created by the use of flat panel video
displays and small video cameras. The most practical sources of natural
lighting will be via thick skylights made of fiber optic composite concrete
like the recently introduced Litracon, light gathered by heliostats and
piped in by fiber optic cable, or similarly piped in by reflective conduits.

So here we find the true challenge to the design of the space settlement.
It's nothing so straightforward as structural technology. Even the
technologies of basic survival in the space environment are a comparatively
minor issue. The really tough part is figuring out how to offer a
comfortable habitat with a potentially unlimited quality of life for the
settler in an exclusively indoor windowless environment -something no one
seems to have ever effectively done here on Earth and rarely even tried. And
this is the show-stopper. If you can't do this there's no reason for anyone
to take a chance on moving to space to stay. This, I suspect, is a key
reason for the waning public support of space programs post-Apollo. There
really have been no compelling and plainly realistic examples of practical
living in space. If the average person cannot picture himself living in
space -that's LIVING, not just visiting- and see a practical personal
benefit to it, why should he care about it except in some low priority
abstract sense?

To date the only examples of life in space are the obviously ridiculous
fantasies of much SciFi and the equally ridiculous sub-duty like existence
demonstrated by the space programs. Right now NASA is investing millions in
an elaborate Mars outpost simulation that will provide a working mock-up of
an actual Mars mission facility on a simulated Martian landscape. That's
fine for selling the public on the notion of manned exploration but in the
end all this will do is impress people with technology while reinforcing the
perception that Mars is not a place 'normal' people would ever be able to go
to live. That ultimately dooms any Mars exploration initiative to the same
fate as Apollo. Once you've extracted all the Big Science out of the planet,
what's left to do if you still don't know how to deploy a habitat better
than an outpost? If you really want people to care about this sort of
endeavor you have to demonstrate some kind of practical liveability. You
have to show people how they can live comfortably there, raise families,
have fun there, do business and industry there, get personal benefit from
being there.

The prospect of having to live your life, cradle to grave, entirely indoors
is troubling in a culture where the only people who normally live primarily
indoors are prisoners, people disabled by exotic illnesses, and the mentally
ill. While in truth most western people spend the majority of their life
time indoors, they don't perceive that as the case since they are so
frequently spending short times outdoors in transit between places and
commonly surround their structures with numerous windows providing outdoor
views. The outside is always immediately accessible and that option is
psychologically important even when it's rarely exercised.

The visionaries of the giant space colony proposals of the 1970s addressed
this problem with a simple notion I refer to as The Great Indoors. Their
strategy was to create a substitute for the outdoors by creating indoor
spaces of such vast scale they could effectively replicate a naturalistic
outdoor environment. They also had another point to this notion; stability.
As anyone who's ever owned salt water aquariums or large hydroponics systems
knows well, larger volume setups are actually easier to manage because that
volume means that chemical fluctuations in the system take longer to have an
impact. So they require less frequent finagling to maintain and provide you
with more time to fix problems when they occur. The same is true of life
support systems in space, making larger scale systems inherently safer and
easier to maintain. The problem with this notion is that it requires
structures of incredibly great size and assumes the ability to fabricate
such structures -things larger than anything humans have ever built before-
all at once in places where no infrastructure at all currently exists.
Assuming such vast construction is possible, the prerequisite infrastructure
necessary for it would take a very long period of time to develop -not to
mention the construction itself. History shows us that most large
communities are not normally planned or designed. They 'happen'. They are
accidental. They are the incrementally developed product of a spontaneous
convergence of individual interests upon a common location offering a
certain set of advantages over other places. Why would space be any
different? For the giant space colony this presents a chicken-or-egg dilemma
that is only resolved by the deployment of some other kind of habitat
capable of incrementally developing the necessary infrastructure for these
big things. Outpost systems can't do that because people can't live in them
long enough. So some other sort of habitat is going to have to provide for
this. Some kind of Not-So-Great Indoors that people would still be perfectly
willing to spend their entire lives in.

Building In Space:

Understanding this situation, where then do we begin in devising possible
compelling yet realistic settlement design strategies. Perhaps we can begin
by looking at the most likely settlement structural systems given the known
technologies and the practical cost and resource restrictions and see what
they have to offer us in terms of a basic habitat.

In space we have two basic environments, surfaces of moons and planets with
some kind of gravity and orbital locations with none. Additionally, those
orbital locations may feature asteroids as sources of structure and material
or they may have nothing, relying entirely on materials brought from
elsewhere, asteroids and space debris being the lowest cost sources. There
remains much debate in the space advocacy community as to whether orbital or
lunar and planetary surfaces offer the best prospects for settlement and
resource exploitation but that debate is moot for this discussion since,
interestingly, the most likely lowest cost structural systems for both
environments result in a roughly similar habitat.

There are basically three commonly described/discussed cheapest approaches
to construction in space. First, one can use unprocessed regolith as a
piled-up shield cover in combination with some simple built-up structure,
such as a corrugated alloy arch, high-pressure rigidized pneumatic shells,
or an 'earth tube' construction system like the Khalili method where tubular
bags are filled with loose regolith and coiled up to form barrel vaults and
domes. A lighter pneumatic enclosure is internally installed to allow
pressurization. This is a very common kind of structure illustrated as
adjuncts to outposts and suggests a likely transition but they are rarely
shown in a significant scale. This approach is unusable in zero-g, since
gravity is relied on to keep loose piled-up shielding material in place.

Next is the use of minimally processed regolith in the form of what we can
generically call 'regolete' which is used to build up or prefabricate rigid
structures which may then be additionally buried in regolith. These may be
purely regolete structures or hybrids combining other structural systems and
materials. Examples include;

-the mass production of blocks which are used to build vaults and domes in
the manner of adobe or CEB construction.

-extruded regolete structures built in the manner of giant
stereo-lithography systems.

-modular cast-in-place systems akin to common commercial construction.

-mound-formed domes and vaults made by piling up loose material into a
desired shape and covering it rough-poured regolete then excavating the
interior.

-the prefabrication of pre-cast regolete chamber modules or modular
components which interconnect to form larger complexes.

-the use of alloy or composite space frame systems which support light
foamed modular regolete/ceramic panels -a most likely approach for
structures in orbital locations.

All these types of structures are then made into pressurized habitats by the
addition of modular pneumatic enclosures or by internal coatings of fiber
reinforced ceramic or epoxy along with prefabricated bulkheads and
hatchways. They are optionally buried in loose regolith depending on basic
shell thickness. Exposed regolete construction has the option to incorporate
fiber optics to make them light transmissive. For pre-cast structures this
could be similar to the current Litracon product. Others would use
formed-in-place fiber cabling linked to heliostats externally and light
emitters internally. These do have the possible option to be image
correcting thus allowing the structure to create apparent transparency, but
the optical component technology for this is speculative.

Finally, there's simple excavation. An area with appropriate geology and/or
pre-existing caves or lava tunnels is excavated with a robotic equivalent of
contemporary roadheader excavator systems, reinforced if necessary with
composite or alloy stabilization pins and/or sprayed regolete materials and
then outfit for habitation with prefabricated pneumatic enclosures,
composite ceramic or epoxy sealant coatings, and prefabricated
bulkhead/hatchway units. Deeper depth hard rock may be impermeable and
massive enough by itself to allow for pressurization with only added
bulkheads. In zero-g, of course, this sort of construction would be asteroid
based.

This latter approach seems by far the most practical long-term because of
the fact that it offers the simplest construction process with the lowest
amount of processing of the indigenous raw material, high structural
versatility, and the lowest demand for manual labor due to easier
application of robotics. It also produces a ready supply of raw material for
further industrial processing. Telerobotic excavation is already a well
developed technology today here on Earth and systems may be easily
repurposed or re-engineered for use in the space environment -even though at
present there has been little interest in this since it doesn't conform to
the common outpost-focussed space development visions. Potentially, habitat
structures can be pre-excavated telerobotically far in advance of any human
presence at a settlement site -a tremendous savings in cost and improvement
in safety by itself. However, excavated settlements have the disadvantage of
being impractical to modify after construction -you can't put rock back
after you excavate it- and so designs must very carefully anticipate long
term reuse of space.

With all these approaches we end up with pretty much the same thing;
networks of simple windowless spaces whose potential sizes and shapes we can
assume to be consistent with that of similar structures here on Earth.
Regardless of the specific structural type, these would all have the aspect
of the excavated structure. And they would all tend to rely on a retrofit
approach to their interior outfitting. The key difference between those in
orbit and those on moons and planets would be that the lack of gravity
allows spaces to have a more volumetric organization with more closely
packed spaces while with gravity one is compelled to use a more
two-dimensional organization with flat sprawling floor planes -except for
the use of free-standing internal mezzanines. In zero-g space use tends to
be more efficient since all surfaces can effectively host fixtures and
furnishings.

Structures relying on prefabricated pneumatic internal enclosures will
likely have a higher degree of compartmentalization with smaller unit
compartments and many more hatchway points, this due to limitations in scale
at which these can be prefabricated and transported through internal
hatchways -an issue which dominates all structural systems and products
which are locally manufactured. Unless your workshop is demountable in
structure, you can only make things internally as big as you can fit through
a hatchway in some manner. They would tend to rely more on secondary
structural framing internally to support their outfitting in order to
minimize possible stress on the skin material, as opposed to retrofitting
systems which place most equipment/component mounting points into the wall
itself using formed-in-place sockets (akin to those of climbing form
systems) or surface-mount attachment points.

Structures using the combination space frame and modular shield panel
systems would likely use a 'pass through' connector on their internal
pneumatic enclosures so that they are fixed to the frame at the space frame
node points and so that these same nodes will interface to internally
mounted equipment and components or possible additional structural members.
In zero-g a much higher uniform rigidity of structure and positive
connection for fixtures and equipment is necessary. Most everything needs to
be rigidly connected to something else. This approach also allows for
structural reinforcement through temporary internal structures when external
components need structural isolation for repair or replacement.

Space Lifestyle:

What can we deduce about likely approaches to the basic layout and
outfitting of these structures? Well, we can deduce one key thing about the
likely general design approach no matter what the construction method; the
space settlement is an urban density habitat. Why? Because of the need to
consolidate life support systems for safety (remember the aquarium
analogy?), minimize the cost of construction by minimizing the need for long
connection points via tunnels, and because external transport has a poor
cost-efficiency due to the space-ship like nature of such vehicles and the
costs of using space suits. So there will probably be no 'homesteading' on
the space frontier as in Earth's past and settlement designs will have to
take into account an orderly and unlimited pattern of expansion from a
single starting point and accommodate ready repurposing of structure as a
settlement grows -especially critical for the excavated settlement which
doesn't have the luxury of reconstruction of older structures.

For interior furnishings the mix of likely low-energy minimal processing
industries suggests a likely mix of basic materials rather similar to that
of traditional Asian and Middle Eastern architecture; ceramics, geopolymers
(Roman cement, Isochanvre), papers and textiles both synthetic and natural
and possibly including animal produced ones like silk, wood substitutes made
of fast growing plants like wheatboard and bamboo laminates, simple plastics
-including polyurethane foams- relying on plant sources, fiber reinforced
epoxies, crude glass, and easily recycled alloys like aluminum recovered
from obsolete outpost structures and discarded components of non-disposable
transport hardware. We would expect these things to be used in as most
efficient a manner as possible and so employ designs based on
interchangeable modular components because it allows for recycling by direct
re-use rather than remanufacture. Minimum Components/Maximum Diversity is
the dominant design philosophy in space. Again, we see a parallel to some
Asian architecture and to low-tech post-industrial building systems like the
Matrix and Box Beam systems. In space metals may be more expensive than
plastics and ceramics because of energy and mining overhead. The most
reliable initial supply of alloys will come from collecting and recycling
the disposable components of spacecraft and the material of obsolete outpost
structures. Consequently, a lot of common hardware such as bolts and other
fasteners would rely on composite, plastic, and ceramic alternatives where
the strength of alloys is not absolutely necessary.

Because surface mounting would be the predominant approach to the
installation of habitat infrastructure systems, inhabitants would tend to
want to conceal these under some kind of secondary wall system, both for
aesthetics and to protect this hardware from accidental damage. But these
would need to allow for much easier access than conventional housing wall
systems and so would be based on modular quick-connect panel systems. This
suggests a 'finished' interior environment covered in modular panel systems
akin to those of the computer room modular flooring or office partition
systems but made of more comforting materials such as textiles and wood-like
materials. Padded panels are especially likely in the zero-g environment.
Many appliances, lighting systems, displays, control panels, etc. would be
expected to integrate into this panel system. Interestingly, here Star Trek
seems to actually get it right, albeit not so much in spectrum of materials.

Life support for the settlement would require systems of great reliability
and long period reserve capacity. Spacecraft life support systems today tend
to be based on fixed reserve systems that are not integral to the design of
the structure, using relatively small components/subsystems. Settlement life
support systems are anticipated to employ Closed Environment Life Support
Systems technologies perpetually recycling air, water, and human waste and
using Living Machine technology that exploits living organisms as the basis
of waste processing. These would tend to feature components/subsystems large
enough to compose major portions of an overall structure. Large chambers
would be used as storage and processing tanks, cultivation units, etc. and
be distributed with fair redundancy across the area of a settlement.

Lighting is the next most critical issue for these windowless structures
-especially when CELSS systems using plants will critically depend on it. We
can expect fiber optics to feature prominently. Why? Because with fiber
optics one can exploit the use of freely placed heliostat systems to gather
and pipe light to where it is needed without large openings into the
structure and because optical fiber -being a spooled material production
process- lends itself to much more compact manufacturing systems than plate
glass. Fiber optic lighting offers greater flexibility in the design of a
settlement and greater adaptability to local conditions. Natural light is
always cheaper than electric light and heliostats can compensate for
differing levels of ambient sunlight compared to Earth through different
sized collection areas. Their light gathering is much more efficient than
windows since they can track the sun as solar panels do. Fiber optic
lighting systems also reduce the amount of wiring and complexity of
electrical systems even when used with electric light sources, reducing fire
hazard, making servicing more convenient (because centralized light pumps
can be placed in more convenient locations), reducing hardware mass (and
hence shipping cost), and increasing energy efficiency and duty life of
electric lighting by as much as 40% over discrete lamp systems.

After fiber optics, electroluminescent lighting systems seems
next-most-likely based on the fact that component mass is low and ease of
transport high, manufacture is lithography-like and can more readily make
use of locally produced plastic or ceramic materials which have a lower
energy cost to process than alloys while their raw materials can be produced
through agriculture. Unfortunately, most all types of lighting system
technology will tend to be difficult to manufacture locally early in a
settlement's development. But the more a fabrication technology is suited to
spooled or sheet materials and lithography-like production methods the
sooner and more easily they can be employed by local small scale industry.

Having some impression of the physical and material composition of the
settlement and logistics of its support, we can hazard guesses at some
cultural and lifestyle elements. For example, the likely easy to make
indigenous musical instruments would be things like bamboo, plastic, and
ceramic flutes, ocarinas, stringed instruments based on composites, and
'salvage' instruments like kalimbas which can be made from salvaged scrap
metals. We can thus readily envision an indigenous cultural 'sound' for a
space community.

Digital media will feature largely in the quality of life of the space
settler. While the cost of import electronics is high, their duty life is
very high relative to that cost by virtue of solid state composition and
they can replace massive volumes of media materials that have a high energy
overhead in both production and disposal. The cost to import digital
information across space is negligible compared to any other kind of import
so digital media, as entertainment, communication, and education, becomes
one of the most cost-effective means of fleshing out one's quality of life
at a low material overhead. Indeed, this is one of the underlying forces in
the current digital media revolution. We are, in fact, seeing a shift in
contemporary culture where an increasing volume of personal property
consists of software rather than physical material. This is especially
apparent among children and the young, the proliferation of toys and sports
equipment of past youth consumers now being supplanted by communications
electronics and downloaded digital media such as music, video, and games.

We can, however, anticipate some significant architectural differences in
the kind of digital electronics employed by space settlements. The current
terrestrial electronics industry tolerates an exceptional
over-specialization in product design and inordinately high rates of product
obsolescence. In space this is not practical. The space settlement lacks the
throw-away consumerist luxury of Earth civilization. It must either recycle
or directly repurpose everything. Electronics systems must therefore follow
the same minimum-component/maximum-diversity design ideology that would
likely be common for all settlement artifacts. So the space settler can be
expected to rely on devices of simpler physical design with higher levels of
functional integration, flexibility, and potential repurposing. This can be
expected to extend to the sub-component level. Current digital systems
design is heavily focussed on application-specific architectures with highly
specialized components. Hence the vast proliferation of specialized CPUs and
system chip sets with high rates of obsolescence. In space it is more
practical to employ digital systems based on hardware of more generic or
homogenous architecture that eliminates the dead-ends of proprietary
hardware or software. So electronics in space will tend to rely on simpler
generic modular circuitry based on things akin to Field Programmable Gate
Arrays where the same simple component can perform a vast variety of jobs
depending on software configuration. These also have the advantage of being
easier to produce with less sophisticated smaller scale manufacturing
systems while not sacrificing potential performance. Indeed, so-called
Virtual Computers based on current FPGA technology already outperform
existing CPUs despite running at circuit clock speeds decades behind the
current CPU technology. The only thing preventing these types of systems
from competing with conventional computers is the lack of a simple mechanism
for self-addressability in the gate arrays to facilitate self-configuring of
processor circuits.

What this all points to is a family of simple electronic devices that are
very homogenous in architecture, relying more on software for capability. I
envision a few sizes of PAD (Personal Access Device -a unit akin to a tablet
computer but relying heavily on network processing power and coming in a
variety of sizes from cell-phone/PDA size to large screen TV size, all with
the same underlying architecture), rack-mounted scalable processors,
networked storage arrays, and small generic 'web controller' units (generic
microcontrollers containing a simple web server hosting virtual control
panels and byte-code command APIs) employing modular software and simple IP
based networks that pretty much do everything necessary in terms of data
processing, industrial control, communications, and personal digital
entertainment. The average person may posses a few different electronic
devices -most likely just several sizes of PAD- that provide virtually all
their personal communications, digital entertainment, and domestic systems
control needs -something that should already exist today here on Earth, if
only the industries involved had any common sense.

Diet in the space settlement will be primarily vegetarian of necessity.
Import of meat products is too expensive while food animals are too resource
inefficient and difficult -if not impossible- to transport through space.
The possible exceptions are some fish, shellfish, and perhaps some insects
-though most people remain averse to the notion of insect foods. These kinds
of animals are more resource efficient and can potentially be transported in
a cryogenically stored embryonic form that allows easy space transport and
can be cultivated without the need of parent animals. Later on, tissue
culturing technologies may allow for production of more conventional meat
products in an industrial laboratory environment without the need for caring
for whole animals, though the products will likely be rather uniform,
clearly different from the 'real thing', and this method of production would
be heavily dependent on sophisticated machinery.

Domestic technology -the hardware of daily life- would have some
interesting, if subtle, differences. Furnishings imported from Earth would
tend to rely on ultra-light designs using knock-down or fold-down packaging
for tight packing and easier space transport. It would tend to have the
aspect of camping gear. Domestic furnishings would tend to rely on simple
modular parts and likewise simple materials commonly produced by the early
industry. They would often be user-assembled and customized, which
facilitates transport through sometimes tight hatchways. These could be
designed to integrate with standardized components imported from elsewhere,
increasing the efficiency of import by limiting it to only those elements
and components which cannot be locally produced. This makes most effective
use of things such as electronics components. There is no need to ship cases
or enclosures for electronics if that much can be readily produced locally,
thus saving mass and import overhead. Organic materials would be favored not
only because of the likely materials available but also because, in the
pressurized habitat environment, industrial hygiene is much more critical.
Chemical outgassing -commonly overlooked as a practical issue for
manufacturers here on Earth- must be strictly limited in space because of
the confined atmosphere and the tendency of contaminants in pressurized
gasses to permeate the human body more readily -something which has already
proven to be a problem with the ISS due to engineers' lack of foresight.

There would be a need to minimize and standardize on the packaging of goods,
eliminating the outrageous level of waste from this common to the
terrestrial consumer culture. It's likely that a small set of standardized
containers made of ceramic, simple glass, or plastics like polyethylene
would be used and perpetually recycled for most goods packaging, storage,
and distribution. This standardization could enable the practical use of
Personal Packet Transport systems, perhaps based on internal railed
transport, integrated into a Personal Rapid Transit system, or using simple
robots. It can also enable the use of robot food processing systems with the
ability to automatically restock foodstuffs through the PPT network, though
such systems would be heavily mechanical and have a high need for alloy
components.

Clothing would, of course, rely on the textiles noted but the perpetually
indoor living would reduce needs to light simple clothing. Sci-fi, of
course, tends to be obsessed with fanciful uniforms. In the realistic
settlement, simpler clothing is more cost effective and easier to recycle.
Wearing little to no clothing at all -at least in private areas- may be an
effective way of making a limited wardrobe last as long as possible when
textile production is limited. Paper and 'felt' like clothing may also be a
distinct possibility since it allows the fabrication of cloths without
mechanical weaving.

The use of combustible gasses in domestic appliances is probably
impractical. Electric appliances would be the norm with sealed element
designs more practical to increase ease of cleaning and prevent the build-up
of food wastes in hidden areas that is common with current primitive kitchen
appliances. Space stations have so far demonstrated a tendency for unhealthy
and potentially structurally damaging mold cultivation. This is a factor
that helped shorten the life of the Russian Mir station. A higher level of
cleanliness for things like food preparation is critical and preparation
methods may be based on a higher degree of ingredient containment and
control to preclude leakage -especially in the zero-g environment.

This need to increase cleanliness and keep fluids under control would extend
also to bathroom/washing facilities. Despite the infamous amounts of money
spent on their engineering, toilet facilities in contemporary spacecraft and
space stations are merely a fancy form of 'packaging toilet' akin to that
envisioned by Buckminster Fuller. This technology may be inadequate for the
permanent settlement. It seems more likely that the same technology employed
for marine incinerating toilets would prove more practical, their dry
sterile output less of a contamination hazard and able to be sent directly
to CELSS systems for processing. But the design of the overall bathroom
facility also needs some attention. Tiles are an easy and likely product for
early settlement industry but have traditionally been a failure for control
of the humidity in the common bathroom, resulting in high levels of mold
growth and a typically high rate of bathroom renovation and repair and
frequent damage to adjacent structures, fixtures, and equipment. They also
are more difficult to clean due to over-intricate shapes. The more practical
bathroom would rely on enclosures with seamless impermeable materials whose
ventilation can be isolated from the ambient air so that moisture can be
completely removed, both through drains and vents. But this does present a
complication in manufacture as large structures -like the increasingly
common prefab bathroom 'ensuite' units- are incapable of being moved through
small hatchways. Perhaps a special variation of the pneumatic shelter module
might be employed to this purpose or surface applied epoxies or cast stone
on modular mesh frames in the manner of ferro-cement construction.

Recreation and exercise in the space settlement may be a challenge but the
logistics seem similar to that of things like cruise liners with similar
approaches likely. Recreational EVA is unlikely unless methods of virtual
EVA using more sophisticated telerobotics approximating a human sensory
experience make it more practical. Virtual exterior spaces in the form of
CAVE (CAVE Automated Video Environments) display rooms based on large area
video window displays may be likely as a crude alternative and if large area
laminate fabricated displays prove economical this could be a common feature
of most individual dwellings.

Exercise is especially critical in the space environment because of the need
to combat the deteriorating effects of reduced gravity. But reliance on
exercise machinery will be more difficult due to their mechanical nature and
subsequent high cost and short duty life. This favors activities like the
martial arts, yoga, dancing, and 'court' sports that rely less on large
spaces and specialized sporting hardware. In line with this would be the
various meditative practices which relate to martial arts and yoga
practices. Swimming and bathing facilities are fairly economical to
implement given a good supply of water and have proven quite practical in
underground buildings on Earth. But they would require the same atmospheric
isolation by seamless enclosure as bathrooms and could not use typical
chemical water conditioning -more likely relying on ozone generators and
reverse-osmosis filtering. In zero-g, mass stability problems with large
liquid volumes makes implementing zero-g pools complicated and possibly
impractical, even though zero-g swimming pools have been a popular idea
among futurists. Accommodating exercise needs may be key in overall
settlement design and considerations of things like running tracks may
feature in settlement layouts. Recreation in general is also critical in
exploiting tourism potential.

In-settlement transportation would primarily be based on simple foot traffic
(or in zero-g, float traffic) which is also an aid to exercise. Settlements
will be dense -arcology-like- but as they become larger in area a need for
assisted transportation between points in a community or distant settlements
may become necessary. Some may feature 'roads' in the form of long tunnels
either excavated or formed of regolith covered arches. These may accommodate
mechanized vehicles, but the relatively high cost and thus scarcity of
alloys and the scarcity of large scale industrial machinery will make
conventional vehicles very expensive. A key exception would be human powered
vehicles like handcarts and bicycles which can be made of composites or even
minimally processed bamboo. Plastics, ceramics and composites are also
suited to the fabrication of electric and pneumatic motors, greatly reducing
the necessary volume of alloys in a vehicle and allowing for supplemental
power to be easily added to these simple human powered vehicles. Segway like
vehicles also seem likely and larger -but still relatively small and light
by Earth standards- car-like vehicles akin to golf carts or 'Smart Cars'.
Fuel vehicles would, of course, be impossible to use internally in a
settlement unless employing closed-cycle systems. Pneumatic, electric, and
human power are the most practical portable power options.

External vehicles are likely, being a logical carry-over from exploration
programs, but they will tend to be large and costly because of
spacecraft-like design and thus relatively few in number and inconvenient to
use. Their role would be primarily in the maintenance of external systems,
support of soft-lander vehicles, the gathering of rough-landed cargo from
drop fields, regional prospecting, and industrial support. Most larger
vehicles may be primarily or optionally telerobotic, used to
supplement/assist telerobotic robots and with seating and controls for
humans used only optionally. This also provides the safety factor of
allowing a vehicle to be driven home by remote control should its operator
become impaired.

A likely early rail transport system on lunar and planetary surfaces would
be a variation of the common 'banana monorial' employed in agriculture.
Banana monorails use an alloy arch support system from which a welded thick
wire 'rail' is suspended. This supports a simple self-contained tractor
based hanging car system or -in the case of the banana plantation- a train
of hooks on which cargo is hung. Similar systems are often deployed in mines
today which makes them a logical addition to an excavated habitat.
Components for these are compact and potentially easy to ship prefabricated
from Earth and can be deployed with simple equipment. But this too would
tend to be used more often un-manned as a means of cargo transport, except
when used internally. This may evolve into a standard Personal Rapid Transit
system using specialized transport conduits as part of the settlement
design.

In zero-g internal mechanized transport would be very different and this is
an issue that hasn't been studied much by designers or even science fiction
writers. It is likely that in larger settlement environments that most
people would wear or carry some kind of personal pneumatic thruster similar
to that used by some free-moving service robots. But these would only be
used for getting around in very large spaces where there is a lack of
hand/foot holds and one has accidentally become 'stuck' in a large open
space. They would lack the propellant capacity to be used as a long distance
means of travel. Ducted fan or compressed air thrust vehicles are a likely
technology but the lack of friction in the zero-g environment makes the use
of large vehicles especially hazardous unless they are 'railed' and have
some kind of positive interface to the structure to limit their range of
movement. Elevator like transport systems seem likely, however, passengers
of such vehicles must be tied down and would be subject to uncomfortable
force on their restraints as vehicles accelerate, decelerate, or change
direction. The human body is designed to resist force most comfortably
through the legs, as it does walking or jumping. But if held in a fixed
position by harness or restraint a traveler in zero-g vehicle is subject to
forces on different parts of the body. The higher the travel speed or
shorter the rate of deceleration/acceleration, the more this becomes a
problem. A form-fitting whole-body enclosure restraint could be too
claustrophobic but would at least be easier to get in and out of than a
flexible harness and be more comfortable than a rigid restraint like in a
roller coaster. A carriage or seat that can rotate during transport to
direct the passenger feet-first or seat-first into the vector of inertia is
another possibility but its frequent rotation would be very disorienting and
the mechanism for this large and intricate. This remains a very open issue.

External vehicles in the zero-g environment are essentially spacecraft,
differing only from others in the kind of propulsion they use and the
capacity -if any- for life support. Because the orbital settlement is likely
to be more self-contained in structure and relies on materials either very
local or very distant, there is no need for the sort of intermediate range
transport represented by typical wheeled external vehicles on a planetary
surface. Most local external vehicles here would consist of telerobots
relying on compressed gas propulsion or point-to-point movement between
attachment fixtures or along tracks which perform exterior maintenance and
construction functions. Other vehicles would be true spacecraft of more
specialized function and much longer range.

We can also hazard a safe guess at the most likely basis of work in the
space settlement. Just as on any frontier, agriculture will be the most
important and therefore the most common form of work. Agriculture is the
most immediate way of processing indigenous materials for practical use and,
of course, is critical for survival. But it will take a very different form
in this environment, being much more industrial in nature since it would
rely on intensive high-density hydroponics methods performed in an
exclusively indoor environment. There seems to be a common depiction today
of 'space gardens' consisting of small inflatable greenhouses. This seems
very obviously an impractical vision, knowing what we know about real-world
agriculture and the volume of it necessary to support the terrestrial
civilization. Obviously, the settlement's agricultural systems must be
pretty vast, are going to be as sheltered from the outdoors as any other
part of a settlement, and very intensive in method. A terrestrial analogy
can be found in the containerized hydroponics systems of the OrganiTech
Corp., though in a zero-g environment ones options are more limited to
pressurized Nutrient Film Technique and 'aeroponic' methods.

On Earth agriculture is primarily concerned with food production, its more
industrial applications often being based on exploiting the waste products
of food production. In space agriculture would be relied on to directly
produce a great deal of industrial materials, providing alternatives to
machine-dependent production methods. It may even be the basis of regolith
mining operations through the use of phytomining or bacterial and
algae-culturing techniques and may be employed to directly produce plastics
such as polyethylene using genetically modified species that can cultivate
such polymers in their tissues. Agriculture may also be a key source of
fundamental life support commodities and vehicle fuels (hydrogen, methane,
and alcohol can be mass produced by agriculture) as well as an integral
element of recycling through Living Machine processing -a strong focus of
current Closed Environment Life Support Systems research. Preference would
be given to fast growth high density species suited to tissue
culturing/cloning techniques, since it may not be possible to rely on insect
or manual/mechanical pollination. Hence the prediction of common materials
for interior finishing like bamboo, hemp, textiles, wheatboard, paper, etc.

After agriculture, mining is the next most common industry -greatly
overlapping with agriculture because of the use of bacteria and plant
cultivation techniques as a low-energy low-machinery means to material
processing. Mining will not only be necessary for the acquisition of typical
mined products as on Earth, it will be a key source of elements for life
support like water and oxygen since in space these exist mostly locked in
ice or mineral forms. Again, early industry will favor things that can
exploit minerals with the simplest processing and least energy. Hence the
preference for ceramics over alloys which have a very high energy overhead
for their production.

Mining operations on planets and moons would rely primarily on the use of
telerobotics just as settlement construction would, possibly employing the
exact same hardware. With orbital settlements, mining becomes a much more
sophisticated endeavor spread over a very large area of the solar system,
unless the settlement is relying exclusively on materials from an asteroid
it is located on. Long distance remote prospecting, mining and transport
must be managed across vast regions of space and encounters problems of
communications latency -making telerobotics difficult- and extremely
protracted transit times. It remains an open question whether it is easier
to try and capture and transport whole smaller asteroids to close orbital
proximity of a settlement or to excavate them in place and transport bulk
material to the settlement via trains of small transport vehicles, unpowered
containers, rigid blocks of semi-processed material, or as streams of loose
granular material just thrown into space by mass launchers. One interesting
possibility is the use of a speculative technology known as laser molecular
conveyance which uses a tuned laser beam to transport material
point-to-point in molar stream form traveling at near-light speeds. This
technique would also allow for the multiplexing of different materials
streams which are sorted at the receiving end by switching systems akin to
those of telecommunications systems.

Smelting processes and other similar basic mineral processing methods would
tend to rely either on solar thermal systems or on compact microwave based
systems. Mass distillation technology has often been speculated by futurists
and is especially suited to the environment of orbital locations and to the
possible combination with laser molecular conveyance. Essentially, it would
rely on solar power to atomize powdered materials in the manner of a
laboratory mass spectrometer but at vastly larger scale. The resulting
individual ionized atoms sort themselves out by atomic mass along an
evacuated column, precipitating in mono-molecular forms along its
cryogenically cooled walls to be scraped off for collection. This technique
has the advantage of providing a single method for the refining and
recycling of all matter but its energy overhead is so exceptionally high
most engineers are dubious about it's practicality. More recent speculation
has focused on a nanotechnology alternatives based on the use of nano-chip
array materials processors which extract discrete molecular species from a
homogenous 'soup' of materials in liquid suspension. Of course, similar
techniques are already employed by many organisms which can be exploited
with relatively simple systems, algaeculture in particular offering a
variety of lithophoric species able to extract useful minerals from aqueous
solution.

After mining comes basic industry. Virtually all initial industrial
production would be conducted at the post-industrial or 'garage shop' scale,
limited to tools and systems that can be easily transported from Earth or
made locally and which can do things with great energy and labor efficiency.
This greatly limits the sophistication of goods that can be made early on,
especially at current technology. However, the post-industrial technology
trend here on Earth does continue to advance steadily and we can expect
production capability to steadily increase in sophistication for facilities
of this small scale. On Earth, the number of products that absolutely
require industrial facilities of great scale to cost-effectively produce is
shrinking steadily. Still, one must anticipate considerable limitations for
the initial industrial facilities of a settlement. And there is also the
simple but critical limitation that one cannot make anything whose
components are larger than what can be fit through available hatchways
unless the work enclosure -and all the tools used- are completely
demountable.

We've already discussed the common materials much of this early industry
would be based on. For technique, existing small scale industrial technology
favors methods using variations of lithography, small scale machine tools,
various forms of stereo-lithography and rapid prototyping, materials in
spool, sheet, liquid, and granular forms, and general industrial design with
a high reliance on the minimum-component-maximum-diversity philosophy of
modular design. One key exception, though, may be arts and crafts. Artifacts
of these kinds may -for a time- have a disproportionately high market value
on Earth and become the basis of a small export market. Likewise, artists
materials originating in space. This is probably not a sustainable market
because it is novelty based and there is basically nothing in practical
value such goods made in space could add over their terrestrial
counterparts. (as opposed to things like semiconductors, optical fibers,
pharmaceuticals, cultured tissues, organs, limbs, nanomechanisms, etc. where
a microgravity and high vacuum environment offer unique processing
potential) So in the long term the bulk of industrial production will be for
a local market.

Impressions: The Outside Indoors

Taking all this information into consideration, we should have a fairly good
picture of the general situation of space settlement. Where does this lead
us in terms of settlement design strategies? The overriding issue here is
overcoming the negative perception of a perpetual interior existence. The
contemporary examples of underground architecture suggest three basic
elements as necessary to combating claustrophobia and the general sense of
indoor confinement, though to date most such architecture has had very
limited success addressing these issues. These three elements are light,
clear-span area, and the presence of naturalistic environmental elements
such as plants and water.

Perhaps the most audacious example of an attempt at a 'luxury' underground
habitat that is also close to the space settlement model is the Henderson
House in Las Vegas. Consisting of a 16,000sf vault 25 feet below the ground
and with no windows, this house attempted to recreate what was essentially a
conventional luxury ranch home and lot property within this completely
enclosed space. It was probably the best one could do with circa 1960s
technology and remains unsurpassed today in many ways. The home consisted of
a simulation of a house structure on a simulated grass lot complete with
artificial lawn, trees concealing structural columns, swimming pool, and
rock garden. A sophisticated computer controlled -but unfortunately not full
spectrum- lighting system provided a simulation of natural daylight cycles.
A sound system provided simulated outdoor ambient sounds and a vast painted
landscape provided a crude illusion of outdoor views from the house windows.
The ranch home design made every attempt possible toward being normal -well,
at least as 'normal' as upper-class Americans with a Las Vegas taste in
design could manage.

The Henderson house was both a success and a failure. It succeeded in being
popular as a party center for the Vegas celebrity elite for a long time and
is still popular today for events. And it served as a comfortable home for
many years. But it was ultimately a failure as a prototype for a line of
such luxury homes as was originally intended. It was never duplicated
elsewhere. The attempted simulation of a conventional house in an outdoor
environment was appreciated for its novelty and cleverness but was a failure
as an effective simulation. It could not sustain natural plants due to the
inadequate lighting technology of the time and its simulation of flora was
unconvincing and perhaps alienating to many in its obvious artificiality.
It's mural covered walls and accent lighted ceiling were not an effective
substitute for real exterior views and could not conceal the basic
rectilinear shape of the large vault. It may have been more effective given
the greater talents of true Trompe l'oeil artists or perhaps the use of
back-lighted photopanoramas but it clearly had its practical limits.

A few more modernist underground homes have explored the concept of the
periscope window or 'view plenum' as a means to provide exterior window
views along with ambient light for underground homes with similar complete
underground enclosure. Such windows are quite effective at creating the
illusion of a normal exterior view and can allow for an effective simulation
of a conventional home layout with varied perimeter wall windows. But they
are not without their complications. They are very expensive -greatly
increasing the amount of material and labor for window construction- and
they require light shafts as wide as their view panes. Deep or large
structures probably could not cost-effectively use these. High cost has made
this approach generally impractical for the majority of contemporary
underground homes. However, the concept has drawn attention from some
futurists speculating on longer term space outpost design.

There is, of course, a long -if not well known- tradition of underground
architecture worldwide and the most common solution to the potential
negative aspects of the underground environment among past subterranean
dwellings has been the use of large or numerous atriums which allow for
ambient light penetration through side or perimeter portals and provide
sheltered spaces suited to gardening or the use of ponds and pools offering
additional service as reflectors of light. An excellent example of this
strategy is seen in the famous Forestierre Underground Gardens in Fresno
California. This is, in fact, a variation of a very common mode of early
urban design derived from the ubiquitous walled compound arrangements of
antiquity. The notion of a home relying on exterior views is a rather
contemporary one deriving from western middle-class attempts to emulate the
estate aesthetics of upper-class housing. For most of human history and in
most cultures the focus of housing was inward, to a central courtyard or
atrium which afforded outdoor ambience with indoor privacy. But these have
had the advantage of actual open space with actual sunlight and very easy
access to the rest of the exterior environment. Still, this is suggestive.
The sophisticated sculptured gardens of walled compound residences in Asia
are legendary for their beauty and seem to offer a level of comfort and
serenity far beyond anything one might see in the micro-estate lot divisions
of western suburbia. With their hand-crafted landscapes and carefully
trained flora, these are environments as artificial as a high-rise apartment
-only the sky is natural- and yet they seem more naturalistic than the
typical untamed suburban back yard.

Another source of inspiration can be found in the design of shopping malls
and in the design of Las Vegas casinos. These facilities are interesting in
that they are complex habitats that completely -deliberately- isolate the
inhabitant from the exterior world, immersing him in an environment tailored
to the stimulation of his consumerist impulses. In both of these kinds of
facilities today we see presented an interesting concept; the indoor
'outside' space. The contemporary shopping mall is largely a representation
of the urban street within an enclosed space. You have 'wings' of structure
where a wide 'promenade' takes the place of the street and is lined in shops
just as any open commercial street in a conventional city -especially the
older European city. Plants and fountains are arrayed along the promenades
and concentrated at intersections of wings in imitation of the public
squares, further reinforcing the illusion of an outside space. In the
largest of shopping malls such spaces can be large enough in area to host
very elaborate public gardens, amusement park rides, swimming pools,
aquariums, and the like. Add hotels and the shopping mall is in effect a
complete indoor city whose inhabitants are perfectly comfortable -at least
within the context of shopping and recreation. And yet there are very few
examples of any developer trying to go that one extra step; to design a
shopping mall as a place to live and work as well as shop and recreate
-though there have been close attempts in the design of some mega-buildings
such as the Renaissance Center in Detroit.

Casinos -the more contemporary ones at least- take a similar strategy with a
greater focus on luxury and comfort since they now commonly integrate a
hotel facility and a very diverse spectrum of recreation. Though their
layouts exhibit much diversity, the notion of indoor outside space is common
and in many cases we see these spaces as the focus of a simulation of the
outside environment complete with free-standing buildings and simulated
skyscapes painted or projected on domed ceilings. These sometimes serve as
stages for elaborate shows -a kind of interior stadium or ampitheater that
may feature simulated night/day and weather transitions as part of computer
controlled audioanimatronic shows. Interestingly, there have even been
attempts to employ this same strategy inside cruise liners and even in the
relatively small spaces of railway passenger cars.

The use of domed or dome-like ceiling arrangements in these artificial
exteriors is significant. Domes have had a similar role in a lot of
architecture. Contrary to popular belief, the fondness for domes in
classical and ancient architecture seems to have had less to do with any
symbolism of the overall round exterior form and more to do with the ability
of this concave interior surface to create the illusion of a skyscape. This
is indicated by the frequent employ of decoration that features sky-like
elements -clouds, constellations- and representations of mythological
creatures or divine beings attributed with a stratospheric domain. The
religious significance is obvious. To enter the domed or vaulted temple
environment is to enter a religiously ordered re-creation of the universe
with its own layered regions of earth, underworld, and heaven. In modern
times the power of the dome to reproduce a skyscape was, of course,
rediscovered with the invention of the planetarium -which is a very
literal/scientific representation of the sky whose overall architecture
often mimicked the temple architecture of antiquity. This power was then
rediscovered again with the large geodesic dome, whose architects were
surprised to discover the readiness of the average visitor to perceive the
translucent surface of the dome as a 'sky' and the interior space as kind of
'outside' in spite of the very obvious artificially of the domes mosaic
appearance. Clearly, a simulated sky doesn't always need to be that perfect
a simulation to create the impression of an exterior space.

Another interesting aspect of the use of domes in antiquity is the common
use of colonnade perimeters which lofted the lower edge of the dome above
the height of the occupant. What is the point of this? Perhaps this was
employed as a means of boundary dissolution; a means to break-up the
visually obvious boundary at the edge of a domed structure to create the
illusion of infinite area. A true sky is unbounded. The horizon is
unreachable and hence the sky is of infinite area. When a dome comes down to
a point on the ground its perimeter is perceived as a wall and the actual
limited volume of its space becomes apparent. But when lofted above
head-level and made permeable by a perimeter colonnade a subtle but
significant illusion of continuance is created, sometimes reinforced by
simple decoration that further conceals or diffuses the physical edge of the
dome. Thus when one enters such a domed space from the outside one can
perceive a subtle integration between the real sky outside and the false one
inside. It's not like you are going indoors. It's like entering an exposed
atrium or courtyard. This seems to work even where the perimeter of the
domed space is not directly adjacent to the exterior but rather surrounded
by rooms. Simply the act of replacing perimeter walls with a transmissive
structure and concealing the edge of the dome from obvious view produces the
impression of an apparent -if unseen- horizon.

Design Concepts: A New Model for the Frontier Home

Putting all these impressions together we arrive at an interesting notion of
a basic design approach for fully enclosed windowless habitats that relies
on a similar tactic of boundary dissolution enhanced by curved ceiling
shapes, lighting, the use of naturalistic elements, and a basic radial
organization centered on large clear-span spaces. To illustrate this, let's
use the model of a private excavated subterranean residence in a planetary
space settlement. The basic structural shape of the excavated space would be
that of a large shallow clear-span domed chamber with a cylindrical
perimeter lofting it one to a few storeys clear.

The center of this space is reserved for a simulated atrium and topped by a
high-brightness diffuse lighting structure with a spectrum full enough to
support natural plant growth. Depending on area, this space could host
artificial landscaping, pools, waterfalls or fountains, small trees, and
perhaps small free-standing decorative structures.

Functional residence structure is formed as a radial series of rooms and/or
an open plan space which opens onto the atrium and can be closed off from it
with translucent sliding screens. A flat suspended ceiling is used in this
surrounding structure and ends in an apparent 'roof' overhang that conceals
the edge of the dome and can be used as a location for lighting fixtures
-assuming a reflective atrium ceiling. Planters for hanging plants,
ventilation systems, possible sprinkler systems for plants in the atrium
space, and extremely quiet fans to create artificial breezes might also be
added above this false roof. The structures of the residence are light. They
have no need to provide functions of shelter from the elements or the space
environment as the primary structure is doing that job. They only serve to
provide privacy, comfort, an attractive appearance, and support for
fixtures. Depending on the ultimate size of the space, multi-storey
perimeter structures could be used with a terraced approach. If the basic
structure cannot support very large spans, a similar approach would be done
with a central domed chamber surrounded by smaller linked chambers of
rectilinear shape.

The larger the span of the central atrium space, the more like an 'outside'
space it would seem since perimeter features would be more diffused by
distance and the obscuring of view by central gardens. This may make it more
effective to employ very large chambers shared by extended families or
multiple households. But this depends on the performance of the structural
system and materials and the difficulty of construction involved. Still,
even in relatively soft excavated materials like salt, football field sized
chambers are not uncommon and concrete domes have to date realized quite
impressive scales. So such areas seem within the realm of common structures.
In the reduced gravity of the Moon and Mars very large spaces seem quite
likely -some scientists even speculating that natural lava tubes of vast
scale may be commonly found. These have actually been proposed as likely
settlement locations but the notion seems to have drawn little interest by
most space enthusiasts or space artists.

Using a radial community organization, such residences would be arrayed
around neighborhood courts based on similar, but perhaps larger, atrium
spaces surrounded by colonnades or facades and perhaps interspersed with
small chamber rooms for various utility or service functions. These could
also be multi-level, using the same terraced approach of multi-storey
residences. Neighborhood clusters could, in turn, be arrayed around even
larger central courts or gardens whose perimeter could also function to
concentrate commercial/municipal facilities.

Using a branching community organization, corridors from individual
residences would open to portals flanking an illuminated vaulted promenade
simulating a 'street' which may feature domed atrium courts at branching
points. The effect would be similar to many European cities and could
likewise feature multiple levels. These streets would, much like their
terrestrial counterparts, concentrate commercial and municipal activities,
provide vias for foot and bicycle traffic, and possibly parallel conduits
-above, below, or to the sides- for PRT or other transport systems and for
key utilities infrastructure.

In a zero-g environment the obvious lack of 'up' or 'down' complicates the
notion of an atrium space and the use of gardens or the creation of
naturalistic landscaping. How then do we manage the illusion of an interior
'outside' space as demonstrated by the domed structure settlements described
above? Again, boundary dissolution is key and to achieve this we can exploit
an optical effect realized by camouflage researchers during WWII. Many
clever camouflage techniques were devised to give military forces an edge in
combat and one of the most unusual was the notion of bright lamps as a means
to make vehicles or structures invisible against the sky or horizon or too
obscured in form to target at night. Glare from such lights diffuses the
visual detail of structures behind them, letting them merge into the diffuse
line of the horizon, the diffuse glow of the sky, or simply blurring out
their outline. Using a similar strategy one might be able to obscure the
surface features and thus the apparent boundary of a large sphere's
interior.

If one creates a large clear-span spherical or spherically-capped cylinder
enclosure in zero-g lighting fixtures are limited to location along its
inner surface. Given a regular pattern of bright diffuse lighting in such a
space, other surface features on the surface become increasingly obscured
the more the curve of the structure brings the cone of incidence of the
lighting fixtures into the field of vision of the viewer. In effect, the
surface detail fades into an apparent skyscape of diffused light. The
smaller and more numerous the number of lighting fixtures and the larger the
space the better this may work. During the night cycle the lighting fixtures
would be dimmed but not fully extinguished which, in combination with the
randomly lit and unlit portals of individual rooms, create the impression of
a star-filled night sky.

Following the example of the previous residential structure, one would then
surround the inner surface with a series of functional chambers which all
open onto or view this central atrium space and can be screened off for
privacy. This breaks up the continuous surface of the sphere into a matrix
of portals in the manner of a colonnade. The interior design of zero-g
habitats has tended to be dominated by one overriding ergonomic factor; the
need to insure ready access to fixed surfaces or hand-holds to prevent a
person from becoming 'stuck' in a space out of reach of anything to grasp
onto or push off of. So most space habitat and spacecraft interiors are
designed such that the maximum width of any space is just a little more than
the average height of a human standing arms-down. Though a large atrium
chamber would defy this convention, residence/functional space would tend to
conform to it. Consequently, the design of individual residence units in an
orbital settlement would tend to take their cues from things like the
Japanese Capsule Hotel using rooms that have a maximum width of about two
meters and which use built-in fixtures on their surrounding surfaces. A
multi-room residence would thus use cellular or 'prismatic' arrangements of
such rooms linked side-to-side by small connecting portals. A honeycomb
arrangement could be likely or some combination of 'tiled' prism shapes and
it seems logical that one could employ virtual windows with exterior views
in displays matching and opposing the portals viewing the interior atrium.

There is actually a very good graphic example of this sort of housing
design, based on single room apartments (a reference to the low-end of
Japanese apartments), portrayed in the hard SciFi Japanese anime series
Planetes. It even shows these arrayed in large residential apartment
clusters surrounding a large open -but dark and rectilinear- atrium space.
Such a design seems practical for early space hotels and also for large long
duration spaceflight passenger vessels using cylindrical configurations
where simple foam mattresses on opposing sides of each passenger 'cabin'
provide convenient resting surfaces during acceleration and deceleration
phases.

The one complication with this approach using a spherical or cylindrical
structure, though, is that it creates numerous irregular interstitial spaces
around the regularly shaped cellular rooms. This could be used to
accommodate utilities conduits of different size but is still ultimately
less space efficient. Perhaps a more efficient approach would be to create
large open-plan 'channels' which are 2 meters high but of any size in depth
or width.

Again following the example of the terrestrial atrium, one might make this
environment seem more naturalistic by adding living plants to its center.
But with no up or down and no surface to 'landscape' a different kind of
gardening would be necessary. To this end one might create a kind of bionic
spherical or cylindrical tree in the center of the atrium space using a
semi-permeable ceramic hydroponic plumbing fixture passing through it -in
effect a kind of pressurized fluid-filled ball or column which the roots of
the plants completely enclose holding them in place. With the lighting fully
surrounding this cluster of plants we establish the basic heliotropic
influence in a uniformly outward direction which should help compel the
growth to the desired space-filling shape. Ducted fans in the atrium surface
or cable-stayed caged fans suspended in the atrium might be employed to aid
in air circulation and to create naturalistic breezes. Thus we have a
visually pleasant garden in the center of our spherical atrium space that
inhabitants can even climb into for recreation and perhaps enhance with
cable-stayed 'seating' points, tethered pathways, or tent-like enclosures.

Again following the example of the planar community structures, a nesting
approach could be employed using these atrium centered spaces, smaller
atrium chambers being tangent to and surrounding other larger chambers or
cylinders arrayed in a branching configuration. Or an organization based on
the closest-packing of similarly sized spheres could be employed. However,
such volumetrically clustered structures could become rather difficult to
navigate when there is no specific hierarchical order of spaces. Then again,
such hierarchical layouts imply very large central volumes which become an
increasing hazard for people to move in, the larger the space the greater
the odds of getting stuck out of reach of hand-holds. It thus becomes
necessary to grid the inner surfaces of the larger spaces with intra-surface
corridors to provide safer vias. To this end the surface of the atriums
would feature a series of ring corridor channels which open to the atrium on
one side, entry doors into homes on the two flanking sides, and utility
fixtures and perhaps automated personal rapid transit ports or slower speed
'tow-holds' (think subway car hand-hold loops that run on a track and pull
persons holding them along at a modest speed) running on recessed tracks on
the inner side. This would keep human traffic away from the view portals of
individual homes and thus increase apparent privacy while providing safe
vias no matter how large the spaces became.

Of course, if one could overcome the problem of chamber scale using this
approach, perhaps it becomes simpler to let a settlement expand indefinitely
as a single vast spherical or cylindrical structure in the fashion of an
Arcology. This would be easy to achieve incrementally by simply creating
successively larger exterior shell structures and dismantling and recycling
older interior ones. (excavated orbital habitats based on asteroids would,
of course, do this through incremental excavation alone) This might be a
straightforward approach to slowly evolving a relatively small initial
zero-g settlement structure into the kind of vast rotating space colony
structure capable of providing artificial gravity.

Conclusion:

As we can see, with a clear understanding of the essential situation of the
space settlement, many potential design concepts begin to become apparent.
And as the above two examples suggest, it actually may be quite feasible to
create a very comfortable, even luxurious, living environment without having
to resort to super-science fantasies. There is clearly much unexplored
potential in this area that a lot of designers and space advocates are
overlooking. And these are habitats that could be very easily demonstrated
right here on Earth in full scale structures. Indeed, since the focus here
is largely upon interior design for windowless habitats, it doesn't matter
too much the type of external structure employed for mockups. Actual caves
and excavations or even just large clear span industrial structure like
warehouses and aircraft hangers over ready locations for very compelling
community simulations. I think it's time designers and space advocates began
a more serious effort toward the realistic portrayal of life in space.

Eric Hunting

hunting@...